A 5-year stability study of common illicit drugs in blood.

The present study was designed to determine the stability of common illicit drugs in stored blood at various time intervals for a period of up to 5 years. The drugs of interest were cocaine and benzoylecgonine, methamphetamine and amphetamine, nonconjugated morphine and codeine, and phencyclidine (PCP). All specimens were from live individuals and were collected in gray-top Vacutainer tubes containing sodium fluoride and potassium oxalate; the tubes were stored at ambient temperature. The results of the study showed that cocaine and benzoylecgonine have poor stability and require quantitative confirmation within a reasonable time period for reliable interpretation. Methamphetamine and PCP were both fairly stable and had a high probability of confirmation upon reanalysis. The stability of nonconjugated morphine showed wide variation throughout the study. Initially, the morphine concentration decreased, then increased at the 3-year interval, and finally decreased at the 4- and 5-year intervals. The significance of the analytical findings are discussed in this report.